The present invention relates to an exhaust silencer suitable for use with portable combustion engines. More particularly, the present invention relates to an exhaust silencer having a size and weight suitable for use with portable motor saws, especially motor chain saws, and which eliminates the potential fire hazard encountered with conventional chain saw silencers.
Silencers for combustion engines utilized as drive motors for portable motor saws, particularly motor chain saws, are subject to strict safety regulations. These regulations require that the temperature at the surface of the silencer does not exceed 288.degree. C., and that the temperature of the exhaust gases at the location of their exit from the silencer does not exceed 246.degree. C. in order to eliminate the possibility of fire or personal injury. It was found that with exhaust silencers having surface temperatures greater than 288.degree. C. and with an exhaust exit temperature of greater than 246.degree. C. wood chips would occasionally be ignited by contact with the silencer or with the exhaust flowing therefrom, presenting a serious hazard to health and property. Heretofore, however, the prior art has been unable to develop an exhaust silencer which conforms to the above-mentioned temperature limitations and which at the same time possesses a size, weight, and ease of production which renders it suitable for use with small combustion engines, and particularly with chain saw engines.